Step 1: Caramelize the Onions

Heat olive oil in a large skillet over medium-low heat.

Add the sliced onions and sprinkle with salt. Stir to coat the onions evenly with oil.

Cook, stirring occasionally, for about 20-25 minutes until the onions are soft and golden brown. If they start to stick, add a splash of water to deglaze the pan.

Optionally, stir in sugar halfway through cooking to enhance sweetness. Set aside to cool.

Step 2: Prepare the Chicken Patty Mixture

In a large mixing bowl, combine ground chicken, garlic, shallot, parsley, grated apple, panko breadcrumbs, cheddar cheese, lemon juice, salt, and pepper.

Mix gently with your hands or a fork until just combined. Overmixing can make the patties tough.

Divide the mixture into 4 equal portions and shape into burger patties.

Step 3: Cook the Burgers

Heat a tablespoon of olive oil in a skillet or grill pan over medium heat.

Add the burger patties and cook for 4-5 minutes per side, or until the internal temperature reaches 165°F (75°C).

During the last minute of cooking, top each patty with a small spoonful of the caramelized onions and an extra sprinkle of shredded cheddar cheese if desired.

Step 4: Assemble the Burgers

Toast the burger buns lightly for added texture.

Spread your preferred condiments on the buns.

Layer the bottom bun with lettuce, tomato slices, and the cooked burger patty.

Add the top bun and serve immediately.